Space discharge device



P. L. SPENCER SPACE DISCHARGE DEVICE Sept. 24, 1946.

Filed June 7, 1945 2 Sheets-Sheet 1 r L. SPENCER SPACE DIS CHARGE DEVICEse a 24, 1946.

Filed June 7, 1945 2 Sheets-Sheet 2 imam-0 PERCY Patented Sept. 24, 1946SPACE DISCHARGE DEVICE Percy L. Spencer, West Newton, Mass, assignor toRaytheon Manufacturing Company, Newton, Mass., a corporation of DelawareApplication June 7, 1943, Serial No. 490,113

This invention relates to a magnetron, and more particularly to amagnetron in which the dimensions of the internal Structure determinethe frequency of the oscillations produced.

In magnetrons of this kind it is often difiicult to construct thecomponent parts thereof within sufficiently accurate limits which willproduce a desired frequency within narrow limits,.particularly when theoscillations generated are of extremely short wave lengths of the orderof centimeters. Therefore it is desirable that some arrangement bedevised for adjusting the magnetron after it has been completed to bringits frequency of oscillation to an exact predetermined value, eventhough in the initial form of the magnetron said frequency may deviatesomewhat from'said predetermined value.

An object of this invention is to devise a magmatron of the foregoingtype in which simple but efieotive adjusting or tuning means areprovided. Another object is to accomplish the foregoing 7 Claims. (Cl.250-275) with substantially no increase in the complexity of the tubestructure so as to make the tube completely interchangeable with thoseforms which do not contain such an adjusting or tuning arrangement.

The foregoing and other objects of this invention will be bestunderstood from the following description of an exemplification thereof,reference being had to the accompanying drawings, wherein:

Fig. 1 is a vertical section through a magnetron incorporating myinvention;

- Fig. 2 is a cross-section taken approximately along line 2-2 of Fig.1, with certain parts there-' of broken away; and

' Fig. 3 is an enlarged section of a detail of the supporting structureat the top of the cathode shown in Fig. l.

The magnetron illustrated in the drawings comprisesa tubular envelope Imade of a cylinder of conducting material, such as copper. The ends ofthe envelope are covered by caps 2 and 3 likewise formed of conductingmaterial, such as copper, and hermetically soldered in place on the endsof the envelope I. The envelope I is formed with a central annularprojection 4. A plurality of radial plates 5 are soldered in place alongthe inner surface of the projection 4. These plates may be stamped outof a sheet of highly-conductive copper. The inner ends of the plates 5form anode faces which cooperate with a cathode 6 supportedsubstantially centrally of said anode faces. The cathode 6 is preferablyof the indirectly-heated oxide-coated thermionic type having an outerconducting cylinde coated'with electron emissive' oxides and having.

an internal heater, the end conductors I and 8 of which project from theopposite ends of the One of the conductors B cathode structure 5. may beelectrically connected to the external cathode sleeve, while the endconductor I isinsulated from said sleeve. Light conducting shields 9 andI0 may be supported adjacent the upper and lower ends of the cathode 6so as to prevent electron beams from being projected out toward the endcaps 2 and 3. The cathode 6. is supported by a cathodeand heaterlead-inconductor II Welded to the end conductor 8, which as describedabove is electrically connected to the cathode and to one end of thecathode heater. The lead-in conductorI I is sealed through 'a glass sealI2 mounted at the outer end of a conducting pipe I3 hermeticallyfastened through the wall of the envelope I adjacent the lower endthereof. A

second lead-in conductor I 4 is sealed through a;

similar glass seal I5 mounted at the outer end: of a conducting pipe I6likewise hermetically sealed through the wall of the envelope I atthe'upper end thereof. The inner end of the lead-in con-1 ductor I 4carries a connecting rod H, the outer,

end of which in turn carries a split sleeve I8: As shown in Fig. 3, thesplit sleeve I8 surrounds the end conductor 1 snugly so as to afforda'supporting and steadying action-to the upper end of the cathodestructure. However, the engagement be the en'd'conductor l, a flexibleelectrical connect-' er I9 has one end thereof welded to the endconductor I and the other end thereof welded to the rod I'I.

When such a magnetron is placed between suitable magnetic poles 20 and2| to create a longitudinal magnetic field and the device is energized,oscillations are set up. These oscillations may be lead out from thetube my means of a coupling loop 22 extending into the space between twoof the plates 5; One end of the coupling loop 22 is connected to theinner end of a conducting pipe 2" hermetically sealed through the wallof the envelope I substantially midwaybetween the ends thereof; Theotherend of the coupling loop 7 22' is connected to a conductor 24 whichpasses through said pipe 23 and is sealed through a glass 23 is brokenaway at its central portion, but it is understood that said pipe may besubstantially of the same length as the pipes l3 and [6 of Fig. 1. Anadditional conducting pipe, not shown, may be electrically connected tothe pipe 23 and form with the conductor 24 a concentric line throughwhich the high frequency oscillations generated? by.:- the wmagnetronmaybe: conducted: to a suitable utilization circuit.

Each pair of anode arms together with the portion of the projection 4between them form an oscillating cavity. A capacitance exists be-. tweenthe cathode B and the end faces of the anode arms 5. Alsocapacitancesexist between the side walls of each oscillating cavity. The

conductive path around each cavity afforded by the side walls thereofconstitutes an induct,anc e.,

The anode, therefore, is so designed andspaced relative to the cathodethat the inductances andcapacitances described constitute tunedcircuits. I-t-i-s desired that thesecircuits Shall be resonant at 'adefinite predetermined frequency at which the: device is to be operated.The device is in? tended to operateso that each oscillating cavity istuned to the frequency at which each of the other oscillating cavities.oscillate.

It is often difiicult to predetermine th'e dimensions ofthe structure soas to cause the anode structure to oscillate at exactly the desiredpredeterminedfrequency; However, means maybe provided wherebythe normalfrequency of oscillation of the magnetron can be adjusted over a fairlywide range even after the magnetron has been completed. For example, Ihave described and claimed a tuning arrangement in my copendingapplication, Serial No. 425,071, filed December 31 1941. In accordancewith my present invention, this type of tuning is utilized in anarrangement which is of simplified but nevertheless efiectiveconstruction. In order to produce such tuning, a light flat metal rin26. is held in juxtaposed position adjacent the inner ends of the anodearms; 5. The ring 26 is supported by the innor end of the rod 142' bymeansof a connecting member 21' welded to the ring26 and to the leadinconductor M. In order to adjust the position of the ring 25,the pipe l8may be bent slightly. It. will be noted that the lead-in conductor I4 issupported by the seal I5 at a point considerably removed from theposition at which the ring 26 is connected to said lead-in conductor.Therefore, a slight. bending ofthe pipe 16: will produce a relativelylarge movement of the ring 26*. Such bending: of the pipe l6 gives apermanent set thereto, and fixes the position of' the ring 26 inits-proper relation with respect to the anode arms 5 so asto result inthe desired tuned condition of the magnetron structure. As alreadypointed out, during this movementof' the lead-in conductor M, the splitsleeve I 3 slides on the end conductor 1 and in the final position ofadjustment forms: a support for the upper end of the 'catrhode tructureso that in conjunction with the-support afiorded by the lead-inconductor I I, the; cat-node structure is rigidly andaccuratelysupported in place.

Itwill' be noted that the adjustment or tuning described above is in thenature of a factory adjustment to be made at the time that the magnetronis completed in the factory. It will further be noted that when the tubeis completed, it is identical, in; so far as; outside appearance anddimensions are concerned with tubes which do not have such atuningadjustment. Therefore, be m de in a cordance wi h my invention arecompletely interchangeable with such other tubes. However, byincorporating my invention in the structure, a sufiicient degree oftuning is afiorded, so that those tubes, which otherwise might deviatefrom the desired frequency to such an extent as to make themcommercially unacceptable, are readily brought into the properrange,thus. greatly reducing the percentage of discarded tubes which otherwisemight exist.

In accordance with my present understanding of the operation of theinvention, varying the position of the conducting ring 26 will vary thecapacitances-of' the anode structure as described Y above, withoutafiecting the inductances thereof to the same degree.

' pacitanoes will tune the natural frequency of the Therefore, varyingsaid camagnetron in the desired manner.

Of course it is to be understood that this invention is not limited tothe particular detailsas described above as many equivalents will sugest themselves to those skilled in the art. For example, the conductingsurface which is moved adjacent elements of the anode structure mightbedisposed adjacent. other portions of said anode structure. Likewise.elements which Vary the inductance of the oscillating portions of theanode structure might be supported and adjusted in accordance with theprinciples of my invention.

What is claimed is:

1. An. electron discharge device comprising an envelope containing-acathode and an anode, said anode having a plurality ofelectron-receiving l portions adjacent said cathode, and a cavityresonator interconnecting each pair of electron-receiving portions, saidcathode having a pair of electrical terminals, said cathode beingrigidly supported within said envelope and provided with an externalelectrical connection for one of its terminals, a lead-in conductor forthe other of said terminals sealed through the wall of said envelope, aflexible electrical conductor connecting said. lead-in conductor withthe other of said terminals, and a tuning member for said cavityresonator carried by said lead-in conductor, the connection between saidlead-in conductor and the wall of said envelope being sufficientlyadjustable to provide an adjusting movement of said lead-in conductorand the tuning member carried thereby.

2. Anelectron discharge. device, comprising an envelope containing acathode and an anode, said anode having a plurality ofelectron-receiving portions adjacent. said cathode, and a plurality ofcavity resonators interconnecting pairs of electronrreceiving portions,said cathode having a pair of electrical terminals, said cathode beingrigidly supported within said envelope and provided with an externalelectrical connection for one of; its-terminals, a lead-in conductor forthe other of said terminals sealed through the wall of said envelope-, aflexible electrical conductor connecting-said lead-in conductor with theother of saidterrninals, and a tuning member for said cavity resonatorscarried: by said lead-in conductor, the connection between said lead-incone ductor and the wall of said envelope being sufiicientlyadjustableto provide an adjusting movement of said lead-in conductor and'thetuning member carried thereby.

3. *An electron discharge device comprising an envelope containing" acathode and an anode, said po ons djacen said thode, nda cavi yresoenator interconnecting each pair of electron-receiving portions, saidcathode having a pair of electrical terminals, a pair of lead-inconductors for said cathode sealed through the Wall of said envelope,said cathode being supported by one of said lead-in conductors rigidlyconnected to one end of said cathode and electrically connected to oneof said terminals, the other of said lead-in conductors being connectedto the other of said cathode terminals by a flexible connection, and atuning member for said cavity resonator carried by said last-namedlead-in conductor, the connection between said last-named lead-inconductor and the wall of said envelope being sufficiently adjustable'toprovide an adjusting movement of said lead-in conductor and the tuningmember carried thereby.

4. An electron discharge device comprising an envelope containing acathode and an anode, said anode having a plurality ofelectron-receiving portions adjacent said cathode, and a cavityresonator interconnecting each pair of electronreceiving portions, saidcathode having a pair of electrical terminals, a pair of lead-inconductors for said cathode sealed through the wall of said envelope,said cathode being supported by one of said lead-in conductors rigidlyconnected to one end of said cathode and electrically connected to oneof said terminals, the other of said lead-in conductors being connectedto the other of said cathode terminals by a flexible connection, and atuning member for said cavity resonator carried by said last-namedlead-in conductor, the connection between said last-named lead-inconductor and the wall of said envelope being surficiently adjustable toprovide an adjusting movement of said lead-in conductor and the tuningmember carried thereby, said last-named leadin conductor having a memberin sliding engagement with a portion of said cathode forassisting in thesupport of said cathode in the adjusted position of said last-namedlead-in conductor.

5. An electron discharge device comprising an envelope containing acathode and an anode, said anode having a plurality ofelectron-receiving portions adjacent said cathode, and a cavityresonator interconnecting each pair of electronreceiving portions, saidcathode having a pair of electrical terminals, said cathode beingrigidly supported within said envelope and provided with an externalelectrical connection for one of its terminals, a lead-in conductor forthe other of said terminals, said lead-in conductor extending tensionbeing capable of being bent into predetermined set positions to providean adjusting movement of said lead-in conductor and the tuning membercarried thereby.

6. A magnetron comprising an envelope con-' taining a cathode and ananode, means for producing a magnetic field about said cathode, saidanode having a plurality of electron-receiving portions adjacent saidcathode, and a cavity resonator interconnecting each pair ofelectronreceiving portions, said cathode having a pair of electricalterminals, said cathod being rigidly supported within said envelope andprovided with an external electrical connection for one of itsterminals, a lead-in conductor for the other of said terminals sealedthrough the wall of said envelope, at flexible electrical conductorconnecting said lead-in conductor with the other of said terminals, anda tuning member for said cavity resonator carried by said lead-inconductor, the connection between said lead-in conductor and the wall ofsaid envelope being suificiently adjustable to provide an adjustingmovement of said lead-in conductor and the tuning member carriedthereby, I

7. A magnetron comprising an envelope containing a cathode and an anode,said anode having a plurality of electron-receiving portions adjacentsaid c athode, and a cavity resonator interconnecting each pair ofelectron-receiving portions, saidcathode having a pair of electricalter-' minals, said cathode being rigidly supported within said envelopeand provided with an external electrical connection for one of itsterminals, a lead-in conductor for the other of said terminals,saidlead-in conductor extending through a seal mounted at the outer endof a tubular extension mounted on said envelope, a flexible electricalconductor connecting said lead-in conductor with-the other of saidterminals, and a tuning member for said cavity resonator carried by saidlead-in conductor, said tubular extension being capable of being bentinto predetermined set positions to provide an adjusting movement ofsaid lead-in conductor and the tuning member carried thereby.

. PERCY L. SPENCER.

